The present invention relates to a fluid transfer device for transferring a fluid between the device and a subject, and in particular the invention relates to a transfer device for delivering an active substance from the device to a subject intradermally, transdermally, subcutaneously or intramuscularly. The invention also relates to a transfer device for drawing a fluid from a subject. Such devices may be micro-needle devices or otherwise. The invention also relates to an active substance cartridge containing an active substance for use in such a fluid transfer or micro-needle device, and the invention also relates to a method for controlling the pressure at which an active substance is delivered to a subject from a fluid transfer device, such as a micro-needle device.
Micro-needle devices are commonly used for delivering a medicament in fluid form, typically, in liquid form, intradermally, transdermally, subcutaneously and intramuscularly to a subject. Such micro-needle devices, in general, comprise an active substance layer, which typically is of a polymer material defining a first major surface and a second major surface. A plurality of bores, in general, cylindrical bores extend through the active substance layer from the first major surface to the second major surface to form respective active substance chambers for holding similar or different active substances to be delivered to a subject. The bores which form the active substance chambers, in general, are arranged in the form of a matrix.
A needle support layer comprising a plurality of micro-needles extending from a first major surface of the support layer are arranged in a matrix similar to the matrix of the active substance chambers and are aligned with the active substance chambers for accommodating the active substance from corresponding ones of the active substance chambers to the subject. A second major surface of the needle support layer is located adjacent the first major surface of the active substance layer, and a first membrane of a burstable material is located between the second major surface of the needle support layer, and the first major surface of the active substance layer and is sealably secured thereto for sealably closing the active substance chambers adjacent the first major surface of the active substance layer. A plurality of communicating bores extending through the needle support layer extend through corresponding ones of the micro-needles for communicating the active substance chambers with the subject when the first membrane has been burst.
A drive substance layer which defines first and second opposite major surfaces is provided with a plurality of drive substance chambers which are arranged in a matrix similar to the matrix of the active substance chambers, and are aligned with corresponding ones of the active substance chambers. A second membrane of a stretchable material is located between and sealably secured to the second major surface of the active substance layer and the first major surface of the drive substance layer for sealably closing the active substance chambers adjacent the second major surface of the active substance layer and for sealably closing the drive substance chambers adjacent the first major surface of the drive substance layer.
A drive substance, typically, an expandable material which expands under heat is located in the drive substance chambers for urging the stretchable second membrane into the corresponding active substance chambers for pressurising the active substance in the active substance chambers to firstly burst the first membrane adjacent the active substance chambers to communicate the active substance chambers with the corresponding micro-needles for delivering the active substance from the active substance chambers. An activation layer which comprises a plurality of heating elements arranged in a matrix similar to the matrix of the drive substance chambers and aligned with the drive substance chambers is located adjacent the drive substance layer for heating the drive substance contained in the drive substance chambers. A third membrane located between the second major surface of the drive substance layer and a first major surface of the activation layer sealably closes the drive substance chambers.
Such micro-needle devices will be known to those skilled in the art.
However, such micro-needle devices suffer from two relatively serious disadvantages. Firstly, the first membrane of the burstable material which is located between the active substance layer and the needle support layer must be burst adjacent the active substance chamber from which the active substance is to be delivered to the subject in order that the active substance chamber can communicate with the communicating bore of the corresponding micro-needle. The bursting of the first membrane is achieved by pressurising the active substance so that when the pressure of the active substance acting on the first membrane reaches a sufficient bursting pressure, the first membrane adjacent the relevant active substance chamber bursts. However, firstly, there is no guarantee that the pressure of the active substance will be sufficient to burst the first membrane, and secondly, the pressure at which the first membrane is burst may vary relatively dramatically from active substance chamber to active substance chamber depending on the quality and consistency of the first membrane.
A second disadvantage of known micro-needle devices is that it is virtually impossible to control the pressure at which the active substance is delivered to the subject, and thus, it is impossible to control the depth beneath the skin of the subject to which the active substance is delivered to the subject.
These disadvantages are undesirable, and there is therefore a need for a micro-needle device which addresses at least one of the disadvantages of known micro-needle devices.
The present invention is directed towards providing a micro-needle device which addresses at least one of the disadvantages of known micro-needle devices. The invention is also directed towards providing a fluid transfer device for transferring a substance between the device and a subject, and the invention is also directed towards providing an active substance cartridge for use in a micro-needle device or a fluid transfer device. The invention is also directed towards providing a method for controlling the pressure at which an active substance is delivered from a fluid transfer device to a subject.